Evaluation of adsorption and coagulation as membrane pretreatment steps for the removal of organic material and disinfection-by-product precursors

Adsorption using powdered activated carbon and coagulation using polyaluminium chloride or aluminum sulphate were investigated as pretreatment steps prior to membrane filtration to remove organic material and trihalomethane (THM) precursors contained in a raw drinking water source. Ultrafiltration and microfiltration membrane treatment alone could not effectively and consistently remove organic material, measured as total organic carbon, and THM precursors, measured as chloroform formation potential, contained in the raw water. Coagulation, prior to membrane treatment, significantly improved the removal of organic material and THM precursors contained in the raw water. Microfiltration membrane treatment, with pre-coagulation, consistently removed approximately 75% of the organic material and the THM precursors contained in the raw water. A coagulant concentration of approximately 0.3 mg/L, as Al, was sufficient to achieve this high removal efficiency. Adsorption, prior to membrane treatment, did not significantly improve the removal of organic material or THM precursors. Key words: adsorption, chloroform, coagulation, disinfection-by-products, drinking water treatment, microfiltration, trihalomethanes, ultrafiltration.